a. [ L. triennium the space of three years; tri- (see Tri-) + annus year. See Annual. ]
n. Something which takes place or appears once in three years. [ 1913 Webster ]
adv. Once in three years. [ 1913 Webster ]
‖n. [ L., from tres, tria, three. ] (Rom. Antiq.) A Roman copper coin, equal to one third of the